1. Field of the Invention
This invention pertains to the field of measuring systems. More particularly, this invention pertains to systems for measurement of relative motions. Still more particularly, but without limitation thereto, this invention pertains to systems for measurement of head movement of a person relative to their trunk when the person is exposed to sudden accelerations.
2. Description of the Prior Art
Prior attempts to measure relative head motion of a subject during sudden accelerations such as during parachute opening have employed accelerometers. The accelerometers were attached to a subject using a custom formed metal bite plate held in place with a series of straps around the head. A custom molded plastic device placed on the subject's back over the first thoracic vertebra, and held in place with straps around the subject's torso, was used as a torso accelerometer mount. When this system was adapted to gather head motion data during parachute opening tests, the resulting data was difficult to analyze due to uncertainty in initial conditions and cumulative errors resulting from the integration of acceleration data. Also, the safety of the mouth mount in the parachute test environment came into question as a result of instances of chipped teeth apparently resulting from objects hitting the mount assembly.